Why did the supersonic trans-Atlantic Concorde aircraft end up being a huge flop? It is commonly believed that European subsidies don't make for efficient airlines and the cost made it impossible to keep the aircraft maintained - but a new paper by a mechanical engineer says it was...evolution.

Adrian Bejan, professor at Duke University, says that a physics paper he penned more than two decades ago helps explain the change in passenger airplanes from the small, propeller-driven DC-3s of yore to today's behemoth Boeing 787s.

The Concorde, alas, was too far from the curve of these good designs, Bejan says.

This chart says the ratio of mass to speed of animals follows the same general rules as airplanes. The Concorde is way off of the historical trend. Credit: Adrian Bejan

"The evolution of Earth's species occurred on a timescale far too large for humans to witness," said Bejan. "But the evolution of our use of technology and airplanes to transport people and goods has taken place in little more than a single lifetime, making it visible to those who look. Evolution is a universal phenomenon encompassing technology, river basins and animal design alike, and it is rooted in physics as the constructal law."

The constructal law was developed by Bejan in 1996 and states that for a system to survive, it must evolve to increase its access to flow. For example, the human vascular system has evolved to provide blood access to flow through a network of a few large arteries and many small capillaries. River systems, tree branches and modern highway and road networks show the same forces at work, he says.

In the case of commercial aircraft, designs have evolved to allow more people and goods to flow across the face of the Earth. Constructal law has also dictated the main design features needed for aircraft to succeed; the engine mass has remained proportional to the body size, the wing size has been tied to the fuselage length, and the fuel load has grown in step with the total weight.

"The same design features can be seen in any large land animal," said Bejan. "Larger animals have longer lifespans and travel farther distances, just as passenger airplanes have been designed to do. For example, the ratio of the engine to aircraft size is analogous to the ratio of a large animal's total body size to its heart, lungs and muscles."

To apply his theories to airplane design, Bejan teamed up with Jordan Charles, a researcher and development engineer, and Sylvie Lorente, a professor of civil engineering at the University of Toulouse, to mine the historical databases of successful commercial aircraft. As they plotted thousands of statistics including year of introduction, size, cruising speed, engine weight, fuel weight, range, wingspan and fuselage length, many patterns began to emerge.

This graph shows how -- as the years have passed -- bigger and bigger airplanes have joined the ranks of their behemoth brothers. Credit: Adrian Bejan

But two in particular stood out.

In one chart, a clear curve tracks the increasing size of commercial airplanes through nearly a century of aviation. As time moves on, new commercial airliners come in all sizes but the biggest are joined by even bigger models. In another chart, the line that best tracks the relationship of body mass to airplane speeds is nearly identical to mass and speed statistics from various mammals, lizards, birds, insects and more. Evolutionary constraints found in nature, in other words, can be seen at work in the airline industry.

There was, however, one outlier on the chart—the Concorde.

"The Concorde was too far off from the ratios that evolution has produced in passenger jets," explained Bejan, who points out that the doomed aircraft had limited passenger capacity, a low mass-to-velocity ratio, an off-the-charts fuselage-to-wingspan ratio, massive engines and poor fuel economy. "It would have had to adhere to the constructal design rules to succeed."

Bejan said this analysis shows that the aviation industry has done well with its designs over the decades, and that the trends dominating the industry are indeed the most efficient. They also reveal the general design parameters that future passenger aircraft should follow to succeed economically.

"This study gives the rough sketch of what airplane designs will put you in the game," said Bejan. "For design companies, it is money in the bank."

Jose Camberos, research aerospace engineer and lead of design space exploration at the Multidisciplinary Science&Technology Center of the Air Force Research Laboratory at Wright-Patterson Air Force Base in Dayton, Ohio, said that the work will hopefully give the field better insight into where the design of airplanes is going.

"There is definitely an analogy to be understood and articulated to explain why engines and airplanes are sized the way they currently are and how that has evolved," said Camberos, who was not involved with this study. "By looking at the development of aircraft in a larger context in these terms, it may be possible to gain insights into how best to achieve what nature has been able to accomplish already."

Comments

Not impressed, sorry.

Just because an aircraft deviates from some curve doesn't explain anything. Why would a higher velocity/mass ratio cause Concorde to be a commercial failure? All it says is that Concorde was faster than other planes of the same mass, which was the entire point!

Of all the parameters listed, three explain things quite nicely: High mass, poor fuel economy, and limited passenger capacity. A limited number of passengers had to pay a lot of money (for a lot of fuel) to save a few hours flight time across the Atlantic. No fancy "evolution" hypothesis necessary.

I agree, claiming this is the same as biological evolution is a stretch. Aircraft have gotten more optimal while biology has not. Did this engineer look at the human male reproductive system? It is not more optimal at all, it is a relic of our evolutionary past, so regardless of what the exterior looks like, airplanes would only be a facet of evolution if a newer paint job still had a Wright brothers engine.

Nice article. The critical comments by previous commenter, while correct, are maybe a bit harsh. There is no need to use the concept of constructal law to explain the failure of the Concorde, as the commenter pointed out. However, I find it interesting to find that the evolution of commercial aircraft follows a trend that is similar to trends found in nature. All it means is that we get better at designing aircraft for the purpose of carrying the most weight for the least cost. The Concorde example is not really a valid comparison because its design did not fit this purpose. Its aspect ratio wing, engine weight and thrust, and small payload relative to other commercial aircraft are a result of its completely different purpose. Optimized for speed, not payload, naturally it will be an outlier when compared to the likes of Boeings and Airbusses. Its like comparing anatomical statistics of predators like lions or cheetahs to those of grazing animals like bison and cattle. instead, compare the Concorde statistics to those of military aircraft that are optimized for speed and you will find a different evolutionary line upon which it fits quite well. So the premise of the article may be contrived to pique interest and make for a nice headline, its still an interesting idea to make a comparison to nature.

Despite the previous comments, there is a corollary to biological evolution, as there is to all evolutionary principles. As with biology, the key driving force is the "environment" and how we define that context.

In the case of something like aircraft, we would have to make comparable considerations for artificial human selection pressures, just like VHS gave way to DVD, or how cars have changed, etc. etc. etc. Each of these technologies is subject to selection pressures in the "environment" of the consumer and economics.

As a result, we see that technology that doesn't appeal to the consumers will tend to fail, precisely because it is selected against. As a result, one can compare something like aircraft by looking at the selection environment and see whether the abilities scale based on expectations. As pointed out already, military aircraft would have a different criteria for selection than commercial aircraft, because while the latter must be economically viable and depend on consumer spending, the former does not. As a result, success would be measured differently.

As for optimal, that's not even relevant. Many aircraft are also not optimally designed, but they are designed for the purpose they are to serve. As a result, stealth aircraft are considerably less stable than other aircraft, but it works despite not converging on some arbitrary "optimal" standard. So, despite claims that biology is not "optimal", it is optimal enough, because it uses the resources available and it works. You will never see a technical product developed whose sole purpose is to become more "optimal". Unless it offers a competitive advantage in its "environment", it will never see the light of day.

Usually people make faulty comparisons in presuming that even artificial or technical evolution is only seeking to improve efficiency. However, that isn't the case, any more than it is for biology. It is looking to produce the most viable product for the environment (in this case, economics/consumer/military, etc.) and to resolve errors or problems that caused previous versions to fail or become insufficient.

This curve drawn is misleading, and hopefully will not influence anyone in design of aircraft.
several points:
1. living creatures, because of the limitations of transferring blood and nutrients , cannot ( except for microorganisms, use rotating systems. This makes a huge difference.
2. Even more important , at the speed of about 300-340 m/s ( depending on height) the flow changes from subsonic to supersonic, with a large bump in drag( force required to counter viscosity and fly horizontally. Thus the speeds between about 250 and 700 m/s do not behave in similar fashion and cannot be included in a curve like this which assumes a smooth monotonic l change with speed. That is the limitation which really makes an outlier, as only two planes ( the Concorde and the TU144 Concordski ) were ever built, so the curve is biassed .
Fun weekend reading, but not to be taken too seriously

It's interesting how this article supports the "Intelligent Design" theory of creation - both the evolution of the aircraft and creation of living species is no accident but occured because of an intelligent driving force. In the case of airplanes it is man, with creation it is God.

Actually it demonstrates the exact opposite. "Intelligent Design" would argue that the Wright brothers should have designed the 787 immediately. Instead we see the "evolution" of aircraft precisely because the designs were not perfect and needed to change. So, to argue that God is responsible for creation and biological evolution, correspondingly argues that God's design is not perfect and therefore needs to be perpetually adjusted. If that's true, then it seems that God isn't living up to his reputation.

Of course, it's actually much simpler than that, because aircraft [and many other things] are artificial selection and not the natural selection of biological systems. This is readily seen by human artificial selection of domesticated animals, so unless you want to argue that humans "created" German shepherds and Pomeranians, you're misunderstanding the point.about how species evolve. So in one respect you can argue that humans "created" these breeds, but you can't claim that it involved an act of "creation" from nothing.

This is the same problem you run into with your Intelligent Design argument. It is a phony argument, because it is simply a continuation of the creation argument. So unless you're prepared to say that when bacteria become antibiotic resistant, that it is a specific act of God's creation, you're just talking nonsense.

The general notion embodied in Adrian Bejan’s paper is not particularly new. On the odd occasion, over many years, I have come across similar approaches. That is hardly surprising as engineering and technology are evolutionary processes. I looked up Bejan, et al’s, original paper and downloaded the PDF, though have only had time to give it a fairly rapid reading. On that basis, I, broadly, agree with it.

The connection with biological evolution is only an analogy, though it depends how one defines “evolution”, or understands it. Engineering design certainly evolves, as do many other aspects of the art of engineering. Engineers frequently look to nature for inspiration as well as to learn in other ways. Besides, successful engineering works with nature; fighting nature invites disaster.

As far as Concorde is concerned, it is blatantly obvious that it is a bit of an outlier, it always was; we were all aware of that when it was designed and built. The wings were based on that of the Vulcan bomber and the engines were a modified design of the original Vulcan engines. One of the many innovations was air intakes for the engines which slowed supersonic airflow down to subsonic in a distance of about twelve feet, as I recall. Those engineers pushed the aircraft through the air fast enough for the frictional heating to cause it to expand by several inches along its length. I attended a meeting in a terminal at Heathrow in the 1980s and Concorde took off during the meeting. There was too much noise to continue the meeting for a while and the building vibrated; we just broke off the meeting for a while, went to the windows and watched it take off. It hardly needs a graph to demonstrate Concorde was somewhat different to other aircraft. It was a phenomenal feat of engineering and I was fortunate enough to see some of it from “the inside”. On the other hand, many of the works of us engineers are phenomenal.

My understanding of the commercial side of Concorde was that due to initial problems with generating revenues, a British Airways Pilot suggested concentrating on the luxury market. As far as I am aware that market was still strong when Concorde was withdrawn from service with many “up market” users rather upset at its passing. On the other hand, I was rather concerned about safety issues, though my sight of such matters, from the inside, was somewhat secondhand; it was colleagues at British Aerospace who were directly concerned with the design and building of Concorde, rather any direct involvement from me. The Paris crash turned out to be the excuse that was needed to end Concorde’s flying days, though that was, ultimately, down to debris on the runway being thrown up under the wing, causing what turned out to be catastrophic damage.

I note that one person in the comments above, links Bejan, et al’s, paper to “Intelligent Design” and another anonymous person (brave types, are they not?) writes that it proves just the opposite. The statement, “Actually it demonstrates the exact opposite. "Intelligent Design" would argue that the Wright brothers should have designed the 787 immediately. Instead we see the "evolution" of aircraft precisely because the designs were not perfect and needed to change.”, which is complete rubbish. “Intelligent Design” at whichever level one considers it, the physical human sense, or higher, progresses by steps, or rather, it is “intelligent” to proceed with design on a progressive basis. That fits easily with the human sense of the term but slightly different in the higher sense because it is progress over time when there is no time, it all just “Is”; we designed it and created it. Such is the difficulty arising from going into areas one presumes to understand but does not.

Sudden jumps in design, as in the ridiculously extreme example of Wright brothers “Flyer” to Boeing 787, is non-intelligent design because it is not progressive, it is a sudden leap, even assuming the technical knowledge is there to make such a leap. Therein, frequently, lays the problem; non-designers presuming to understand design, as well as, for that matter, non-engineers thinking they understand engineering. That is also why certain pursuits are mislabeled as engineering, genetic engineering, for example; real engineers do not proceed in the ways that many in those fields do.

Actually, the Boeing 787 design is an unusually bold step in aeronautical engineering in that it involves more than one major innovation, for example a composite materials fuselage rather than an aluminium alloy one, as well as electrically powered mechanical systems rather than hydraulic ones.

“Intelligent Design” at whichever level one considers it, the physical human sense, or higher, progresses by steps, or rather, it is “intelligent” to proceed with design on a progressive basis. That fits easily with the human sense of the term but slightly different in the higher sense because it is progress over time when there is no time, it all just “Is”; we designed it and created it. Such is the difficulty arising from going into areas one presumes to understand but does not.

So we create a strawman argument.

Progressive steps occur because there are often gaps in knowledge, so until that knowledge is acquired the initial designs must suffice. This isn't negative, it simply reflects that one can only design/build something based on the current state of knowledge. It is not perfect. The Wright brothers couldn't design or build a 787 because they didn't know how and couldn't know how.

Yet, "intelligent design" advances one specific argument regarding "irreducible complexity", which requires that particular elements of an outcome must be fully designed and implemented without evolution. In other words, there are specific "leaps" that must occur, by definition, which is the entire basis of claiming "intelligent design".

Biology progresses on changes occurring [and sometimes even leaps], while selection affects which of those changes are viable and persist into future generations. Sometimes those leaps occur without gradual change because they may be facilitated by symbionts or even integrated by other mechanisms [for example, symbiogenesis].

So while it may certainly be "intelligent" to progress in steps, presumably you know that that isn't the argument being advanced by Intelligent Design advocates. So while it is clear that aircraft "evolved" from the Wright brothers flier to the 787 through a series of steps, as a result of changes in knowledge and understanding, it most definitely was not formed fully formed as the "irreducible complexity" argument demands. This is precisely why the aircraft example does not support biological intelligent design.

Create a straw man? Not me. I never mentioned Worzel Gummidge, or any of his colleagues.

“Progressive steps occur because there are often gaps in knowledge, so until that knowledge is acquired the initial designs must suffice.”

Not really, knowledge is also acquired by experimenting with different designs. You seem to be out of your area of knowledge and experience.

“Yet, "intelligent design" advances one specific argument regarding "irreducible complexity", which requires that particular elements of an outcome must be fully designed and implemented without evolution. In other words, there are specific "leaps" that must occur, by definition, which is the entire basis of claiming "intelligent design".”

Incorrect; some Intelligent Design proponents put forward the “irreducible complexity” argument but I have never been greatly impressed by it.
I did not even mention “irreducible complexity”. You brought it up. You are the one putting forward a straw man argument.

“Biology progresses on changes occurring [and sometimes even leaps], while selection affects which of those changes are viable and persist into future generations. Sometimes those leaps occur without gradual change because they may be facilitated by symbionts or even integrated by other mechanisms [for example, symbiogenesis].”

I studied for “O” Level GCE Biology, among several other subjects, from 1957 to 1962. I have known the basics of biology for over half a century and added to that during the decades since. As far as I am concerned Bejan, et al’s argument, analogy, broadly holds.

My reasons for accepting Intelligent Design really began in the late 1960s, just after I had entered the engineering profession, at least in terms of being a Higher National Diploma student, or at Brunel University studying for my Degree, I believe the latter and it was while I was home from university; I think it is an incident I included in my forthcoming book. It was a meeting up with former school friends and others in the form of a beach party at Holland-on-sea, Essex. It was a warm evening and, at some stage, I was laying on my back, on the beach, looking up at a clear night sky, just the rustle of the surf, no other lights as the few street lights in that area were kept from sight by the cliff. There was nothing but the sky and stars and that great, crystal clear expanse before me effectively “screamed design”; all of that suddenly arising out of nothing for no reason just did not make sense. That was even at a time when I had difficulty acknowledging the existence of a Creator, though I had never ruled it out, for perfectly logical reasons, I did not have sufficient knowledge to do so. Developments over the next decade, or so, added to that understanding. Rather spectacular events at the beginning of the 1990s took that all very much further. My senses opened up to the extent that I was aware of some of the structures that underpin the physical, without which it would not exist, as well as many events, occurrences at that level. Add to that an expanded reading list and I, eventually, came to understand the nature of the Creator, the Designer; Us. It is rather well encapsulated by a quote from Richard Bach’s book “The Bridge Across Forever”, which I have used at the beginning of my book. There are parallels anyway. Richard Bach is an ex-USAF pilot who made a living “barnstorming”, travelling round the USA giving people rides in his biplane. “The Bridge Across Forever” describes his “normal” life along with other rather different occurrences. My forthcoming book, “Remembering Lorelei”, is also autobiographical and describes my early life, entry into the engineering profession and much of my professional life, along with increasingly unusual events intertwined with it. We both have the same first name, we both have technical backgrounds, we both have a particular relationship with another person and mine in rather unusual, to put it mildly, the person, not quite so much the relationship.

“So while it may certainly be "intelligent" to progress in steps, presumably you know that that isn't the argument being advanced by Intelligent Design advocates.”

I am getting the impression that I know a great deal more about design than you do.

By the way, the above is an indulgence. I enjoy exchanges, debates, as long as they are on a mutual respect level, but my respect for anonymous people is limited and my willingness to engage with them is limited. Soon after this I will be leaving you to your own devices.

Whether you brought up "irreducible complexity" or not, is irrelevant since that is one of the primary arguments advanced by Intelligent Design advocates. It also isn't particularly relevant whether the aircraft analogy holds or not, because that is not an argument that is pertinent to biology. The point was the other way around.

Not really, knowledge is also acquired by experimenting with different designs. You seem to be out of your area of knowledge and experience.

Hence the straw man argument. I certainly never constrained the means by which knowledge could be obtained, but you seem somewhat sensitive to the notion that engineering is not considered science, you presumably excluded that discipline and now want to assert it as a separate, independent source of information. I never suggested that knowledge couldn't be derived from numerous quarters, and it seems intuitively obvious that testing various designs would be fundamental to that objective.

There was nothing but the sky and stars and that great, crystal clear expanse before me effectively “screamed design”; all of that suddenly arising out of nothing for no reason just did not make sense.

For someone that professes to argue that engineering involves as much science as other disciplines, you seem to be quite content to accept personal opinion and anecdote as evidence. So while you didn't feel you had enough evidence to deny the existence of a creator, in one evening you managed to rationalize into existence an entire intelligent designer and creator. Doesn't sound very scientific to me.

In any case, I don't particularly care what you think about anonymous posters nor what you think of the reason for their anonymity. You can either field a pertinent answer to pertinent questions or you can't. Why you elect not to is your own issue to justify.